GEOCHEMICAL CHARACTERISTICS AND TECTONIC SIGNIFICANCE OF THE NEOPROTEROZOIC GRANITES IN NORTHERN DAXINGANLING, INNER MONGOLIA

The well-developed Neoproterozoic granites, broadly distributed in Northern Daxinganling, Inner Mongolia, were formed in three tectono-magmatic stages, with seven rock units. Study on the rock assemblage and geochemistry of the granites shows that, the magma of intermediate-basic complex-granodiorite series in the early stage was derived mainly from upper mantle or lower crust, as the result of subduction and crust-mantle interaction. The magma of porphyritic moyite-monzogranite series in the middle stage mainly originated from the lower crust, being the product of collision-orogeny. The magma of syenite series in the late stage, mainly from the lower crust, was formed in the extensional system in the later of orogenic period. The development and evolution of the Neoproterozoic magmatic rocks has reflected the dynamic characteristics of the south margin of Siberian plate in Northern Daxinganling.